1. Field of the Invention
The present invention relates generally to heating units and more specifically to a free standing heater using forced air.
2. Description of the Prior Art
With the energy crisis a great concern, people have generally been preoccupied with maximizing the use of cheap and inexpensive fuels. A major effort has been made to include heat collectors in fireplaces to collect the heat normally generated by the wood burning therein and to transmit it into the room more efficiently than that provided by the normally designed fireplace. A forced air system in combination with such heat collectors is shown in U.S. Pat. No. 3,896,785.
Even before the energy crisis, people were concerned with the loss of heat escaping through the flue of a heating source. U.S. Pat. Nos. 1,490,135 and 3,094,980 make use of the flue heat in a stove and fireplace respectively to heat a second column of forced air which is introduced into the room in which the stove or fireplace is located.
Prior art space heaters have also been used or converted to fireplaces to provide a pleasing and second mode of heating. An example of this is shown in U.S. Pat. No. 1,944,626.
Although showing many methods of recapture of heat loss by normal fireplace or space heaters, the prior art has not made the most effective use of the heating source. By concentrating their efforts on hotter fires or recapture of flue gases, the prior art has not effectively captured the heat available from the burning material. No effort is made to limit air flow to the fire and up the flue of a fireplace or open fire box except in closed systems with small intake vents.
Thus there exists a need for a system of limiting air flow into the fire box and up the flue for open fireplaces or fire boxes.
Heating units of the prior art have either used the natural upward flow of heating air by drawing cold air in at the bottom of a heating unit to exit heated from the top. Also, forced air systems have been used to augment the natural upward flow by moving more air past the exterior of the fire box. Although the forced air systems have increased the capture of available heat, the prior art devices have not optimized the heat transfer from the burning material in the fire box to the air circulated about the exterior of the fire box.
The natural flow of drawing cold air in the bottom and exiting hot air from the top or just exiting hot air from the top (naturally or forced) creates a hot layer adjacent the top of the room and a cold layer at the floor. Thus there exists a need for a heating unit which maximizes the capture of heat available in burning material and which provides a more uniform temperature in the room.
The build-up of deposits on the exterior of the fire box in prior art devices result from incomplete combustion of the gases from the burning material. These deposits reduce the thermal convection of the heat in the fire box through the fire box wall. Similarly, the loss of these gases up the flue is a loss of an available source of combustion and additional heat.
Thus there exists a need for a fire box which increases heat and reduces deposits.
Another problem with heating units of the prior art is the escape of smoke and other gases drawn from the fire box by the pressure differential produced by rapidly opening the doors of the fire box.